Apparatus for firing ceramic material



Aug. 16, 1938. P. GATZKE 2,126,331

APPARATUS FOR FIRING CERAMIC MATERIAL Filed Dec. 9, 1935 2 Sheets-Shem.1

Aug. 16, 1938. P. GATZKE 2,125,331

APPARATUS FOR FIRING CERAMIC MATERIAL Filed Dec. 9, 1935 2 Sheets-Sheet2 gwuam-foz Paul 609 429 2354;; (QWM Patented Aug. 16, 1938 UNITEDSTATES PATENT OFFICE APPARATUS FOR FIRING CERAMIC MATERIAL Paul Gatzke.Berlin-Pankow, Germany 15 Claims.

This invention relates to a process and apparatus for firing ceramicmaterial and particularly porcelain, hereinafter referred to generallyas ceramic ware, in indirectly heated tunnel furnaces, in which term isincluded electrically heated tunnel furnaces.

In the treatment of porcelain in tunnel furnaces for the purpose ofproducing a spotlessly white porcelain, the atmosphere in the individualzones of the furnace tunnel, that is during the individual phases of thefiring treatment, must be regulated according to accuratelypredetermined condition. As a rule, until the sintering temperature isreached a reducing followed by neutral and finally oxidizing firing iscarried out, but these conditions vary in individual cases according tothe composition of the mass and the kind of material to be fired. Incertain circumstances it may, for example, even be found advisable toreverse the firing sequence, that is to employ at the commencementoxidizing, later neutral and finally reducing firing.

The production of a suitably graded furnace atmosphere presents noparticular diiiflculties in gas heated tunnel furnaces with separatelyadjustable burners hitherto generally used for the firing of porcelain.Also in the case of tunnel furnaces heated with solid fuels it ispossible to attain this by the arrangement of, for example,supplementary firings having a reducing action.

However, difficulties are encountered in infiuencing the composition ofthe furnace atmosphere in electrically and indirectly heated tunnelfurnaces to which the present invention is chiefly concerned, since insuch furnaces, which in themselves produce oxidizing firing and theheating of which does not influence the composition of the furnaceatmosphere, it necessitates a separate introduction of gases exerting areducing effect into the zones of the furnace in which a reducing firingmust be carried out.

This might be effected by introducing suitably composed gases, that isprimarily gases containing C0 for example, in the same way as gasescontaining oxygen, 1. e. air, are introduced into the oxidizing zone,but this presents technical and economical difficulties because thesereducing gases must be procured as such or produced in a separate plant,the working of which requires great care owing to the danger ofexplosion.

Experiments to produce as an alternative carbon monoxide at suitablepoints in the furnace by incomplete combustion of fuels have shown thatthis procedure is not possible without spe- (Cl. 25142i cial measures,because it is neither possible to accurately regulate the 00 content inthe individual zones, as is necessary, nor to produce any uniformreducing atmosphere over the entire cross-sectional area of the furnacetunnel. The reducing gases certainly sweep along the side surfaces andthe upper portion of the charge on the firing truck, but scarcelypenetrate in to the core thereof and consequently a defectively firedarticle results.

These objections are overcome in the best possible technical andeconomical way by the process according to the present invention, whichrenders it possible to feed the reducing gases into the interior of thefurnace at such places and to distribute them so that a reducing actionof the furnace atmosphere is ensured at all points of the whole chargeblock, that is, over the entire cross-sectional area of the tunnel.According to the invention, this result is obtained by the introductionor production of the reducing gases in the interior of the charge in thezones in nich the reducing furnace atmosphere is to be produced, bytransporting through the furnace, by means of the firing truck, areducing gas or a liquid or solid substance which produces the reductiongas by evaporation or incomplete combustion as the firing truck passesthrough the furnace. In the preferred arrangement for the production ofthe reducing gases from liquid or solid substances carried by the firingtruck, the evaporation and the like takes place entirely under theautomatic action of the gradually increasing temperature during thepassage through the furnace, but additional methods of regulation mayalso be provided for this purpose.

In one form of construction according to the invention the platform ofthe firing truck is provided with longitudinal slots or correspondinglyarranged discharge nozzles through which the reducing gas, which as arule is the products of evaporation, gasification or combustion, areconducted directly into the core of the charge.

This is preferably effected by arranging, below a longitudinal slot orthe row of nozzles in the firing truck platform, a storage receptacle,preferably of elongated shape, for accommodating the fuel which ispreferably a liquid gasified by heat. This storage receptacle, althoughit is situated outside the furnace passage proper, heats during thepassage of the firing truck owing to the gradually increasingtemperatures, so that the oil or the like evaporates and the vapor fromthe slot enters the interior of the furnace tunnel and burns exactly atthe place where the reducing gases are primarily needed, namely in themiddle of the charge. In certain circumstances the gradual heating ofthe oil tank works satisfactorily, without auxiliary means, but ifadditional regulation of the existing oxygen content is desired, aparticularly complete evaporation of the oil and consequently anintensive reducing effect of the furnace atmosphere precisely in thezones in which an increased reduction is required can be insured byauxiliary means. It is also possible to obtain this regulation bysuitable selection of the fuel which is to be evaporated. Among thefuels concerned are chiefly liquid fuels such as oils having suitablepoints of evaporation for the case in question. Solid fuels may howeveralso be used. It is also possible to regulate the production of thedesired quantity of the reducing gases in the different zones of thefurnace by subdividing the fuel receptacle under the firing truckplatform, or providing several containers, and filling them withdifierent fuels which evaporate at dificrent temperatures.

According to a further feature of the invention an additional regulationof the evaporation and consequently of the reducing effect may beprovided by fitting in the oil containers or in the walls thereof.resistance heating elements. the heating efi'ect of which is controlledautomatically at the corresponding points of the furnace tunnel, forexample by the terminal contacts of these heating resistances slidingalong contact bars arranged veiow the firing truck platform in thelongitudinal direction of the furnace tunnel during the forward movementof the firing truck. the contact bars being so subdivided and suppliedwith such current that they produce a heating effect of the heatingresistances regulated in steps.

In order to avoid a premature exhaustion of the content of the oil tankwhen there is a considerable consumption of reducing gases, feedconduits for the tanks may be fitted at suitable points of the furnace,through which fuel can be fed during the passage of the firing truckthrough the furnace.

According to a simplified form of the invention the introduction of thereducing gases can be effected alone, or in combination with the abovedescribed method, by providing over the surface of the truck platformcontainers (dishes or the like) for a liquid or solid substance whichproduces such a gas by evaporation (oils, heavy hydrocarbons, substancescontaining waste products,such as waste oll,or mazut (a Russianpetroleum residue or other residue containing oil) said substanceevaporating from said containers sole- 1y under the influence of thegradually increasing temperatures in the individual zones of the furnacepassage as the truck passes through the furnace without requiring anyadditional regulating or heating devices, it being easily possible by asuitable selection or dimensioning of the number, the surface area andthe capacity of the container, to ensure automatic production of thequantity of reducing gas which is necessary in the individual zones ofthe furnace for producing a furnace atmosphere having the desiredreducing composition.

Instead of placing separate bowls, dishes or the like on the firingtruck platform, cup-shaped recesses, may be provided therein having asurface area and depth or capacity according to the requirements of theindividual case.

Instead of providing containers or the like as described above theporosity of the material of which the firing truck platform and otherauxiliary means for firing are made, for example fine clay having a highdegree of porosity, is utilized for accumulating the necessary quantityof substances to be evaporated for the purpose of producing the reducinggases, by saturating the fireclay material with these substances beforethe truck passes through the furnace. The saturation of the boxes,firing supports and other firing accessories in this manner has beenfound particularly advantageous owing to the direct action of thereducing gases.

Besides producing the reducing gases with the aid of the firing truck asdescribed above it is advisable in certain circumstances to provide inthe side walls of the furnace devices for feeding liquid fuels to beincompletely burned also in a suitably regulated manner, for examplepreferably oppositely arranged descending channels which open above thefiring truck platform and to which are fed by ordinary drip lubricatorsregulated quantities of oil. Alternatively a similar fuel introductionis also possible from overhead, that is from the arch of the furnacetunnel using suitable dosing devices. Whether this arrange ment issuitable or whether it is advisable to fit such supplementary equipmentdepends upon the properties of the mass and the structures of thecharge. In certain exceptional instances, for example in the case of acharge built up with wide spacing, or when the absoluteuniformity of thereducing action is not as absolutely essential as is necessary forhigh-grade porcelain, that is for inferior quality fired articles whichmust be fired under similar conditions and to which the invention can beadvantageously employed, it is, in certain circumstances, possible to dowithout the feed of the reducing gases by means of the firing truck andto provide in its stead such a lateral or overhead oil feeding device.

In certain circumstances the slot or the row of nozzles formed in thefiring truck platform may be fed with compressed reducing gas by acontainer arranged under and fixed to the firing truck platform, anautomatic control of the outfiowing quantity of gas being renderedpossible in similar manner by valves controlled by the firing truckpassing through the furnace.

In order that the invention may be more clearly understood oneparticular form thereof (the first form described above) will now bedescribed with reference to the accompanying drawings wherein:

Fig. 1 is a cross-section through the furnace and Fig. 2 a plan view ofa firing truck platform.

Figj 3 is a cross-section through a portion of the furnace to whichindirect heating is applied.

In these drawings a is the furnace tunnel proper. b the firing truck, cthe platform of the firing truck on which the charge at is built up.

A longitudinal slot 9 preferably narrowing towards the top, or a row ofnozzles, (not shown) is arranged in suitable manner in the firing truckplatform. A container 1 which is likewise preferably of elongated shape,is situated below the slot e for the liquid fuel and therein or withinits walls the heating coil 0 is arranged. This heating coil contactswith a collector h which brushes along a conductor bar i divided intosections. Oil feeding devices k are arranged at suitable points at theside of the furnace tunnel a and are provided with drip ollers l whichfeed the oil or other fuel in regulated quantities through inclinedchannels 1:: which open into the furnace slightly above the firing truckplatform. The portion of the furnace which is heated indirectly isindicated somewhat diagrammatically in Fig. 3. In this view the tunnel ais shown covered by a relatively thin wall 0 which is heated from afurnace p. The products of combustion from the furnace p are conductedover wall 0 through a flue q, and from thence through checkerwork r to achimney s. Air is drawn in through checkerwork r and fines t to thefurnace. Any other suitable means may be employed for indirect heatingof tunnel a, or electrical means may be employed which does not affectthe gases in the tunnel.

The invention is not restricted to the forms of construction describedabove and those illustrated in detail in the drawings, but can bemodifled in various manners without departing from the scope of theinvention.

What I claim and desire to secure by Letters Patent is:

1. In apparatus of the class described the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace tosubstantially the desired temperature, a firing truck traversablethrough said tunnel furnace, and means transportable through said tunnelfurnace on said firing truck to introduce reducing gas into the interiorof a charge of ceramic ware upon said firing truck.

2. In apparatus of the class described the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace tosubstantially the desired temperature, a firing truck traversablethrough said tunnel furnace, means constituting a source of reducing gastransportable through said tunnel furnace on said firing truck, andmeans to inject said reducing gas into the core of a charge of ceramicware upon said firing truck.

3. In apparatus of the class described, the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace, a firingtruck including a platform for a charge of ceramic ware and traversablethrough said tunnel furnace and means constituting a source of reducinggas transportable through said tunnel furnace on said firing truck, saidplatform having a longitudinal slot therein through which reducing gaspasses from said source into the interior of said charge.

4. In apparatus of the class described the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace, a firingtruck including a platform for a charge of ceramic ware and traversablethrough said tunnel furnace and means constituting a source of reducinggas located beneath said platform and transportable through said tunnelfurnace on said firing truck, said platform having a longitudinal slottherein narrowing towards the top and connecting with said sourcethrough which slot reducing gas is injected into the core of saidcharge.

5. In apparatus of the class described the combination of a tunnelfurnace. means for indirectly heating said tunnel furnace, a firingtruck traversable through said tunnel furnace, means constituting asource of reducing gas transportable through said tunnel furnace on saidfiring truck and a nozzle connecting with said source through whichreducing gas is injected from said source into the core of a charge ofceramic wareupon said firing truck.

6. In apparatus of the class described, the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace, a firingtruck including a platform for a charge of ceramic ware and traversablethrough said tunnel furnace, a container for compressed reducing gaslocated beneath said platform and transportable through said tunnelfurnace on said firing truck, and means to inject reducing gas from saidcontainer into the core of said charge.

'7. In apparatus of the class described, the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace, a firingtruck including a platform for a charge of ceramic ware and traversablethrough said tunnel furnace, a container for a liquid hydrocarbonlocated beneath said platform and transportable through said tunnelfurnace on said firing truck, a resistance heating element in saidcontainer, a current collector for said heating element, acurrentcarrying contact bar arranged longitudinally of said tunnelfurnace along which said collector slides, and means to direct theheated liquid hydrocarbon in a substantially gaseous state into the coreof said charge where it is incompletely combusted.

8. In apparatus of the class described, the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace tosubstantially the desired temperature, a firing truck including aplatform for a charge of ceramic ware and traversable through saidtunnel furnace and containers upon the surface of said platform for asubstance producing areducing gas when exposed to the heat of thefurnace, said containers being so located that the reducing gas soproduced passes into the interior of said charge.

9. In apparatus of the class described, the combination of a tunnelfurnace, means for indirectly heating said tunnel furnace tosubstantially the desired temperature, and a firing truck, including aplatform constructed of porous material capable of accumulatingsubstances which under the action of heat produce a reducing gas,traversable through said tunnel furnace.

10, In apparatus of the class described, the combination of a. tunnelfurnace including side walls, means for indirectly heating said tunnelfurnace, a firing truck traversable through said tunnel furnace, meanstransportable through said tunnel furnace on said firing truck tointroduce reducing gas into the interior of a charge of ceramic wereupon said firing truck, and means for feeding regulated quantities ofliquid fuel through inclined channels in said side walls, which liquidfuel is incompletely combusted in said furnace to produce a reducingatmosphere. 11. In apparatus of the class described, a firing truckcomprising in combination a truck body including a platform for a chargeof ceramic ware, said platform having a longitudinal slot therein, andmeans constituting a source of reducing gas located beneath said slotthrough which the reducing gas passes into said charge.

12. In apparatus of the class described, a. firing truck comprising incombination a truck body including a platform for a. charge. of ceramicware, said platform having a longitudinal slot therein narrowing towardsthe top, and means constituting a source of reducing gas located beneathsaid narrowing slot through which the reducing gas is injected into thecore of said charge.

13. In apparatus of the class described, a. firing truck comprising incombination a truck body, means constituting a source of reducing gas, anozzle connecting with said sourc e through which truck comprising incombination a truck body including a platform for a charge of ceramicware, a container for a liquid hydrocarbon located beneath saidpiatform, a resistance heating element in said container, a currentcollector for said heating element, and means to direct the heatedliquid hydrocarbon in a substantially gaseous state into the core ofsaid charge.

PAUL GATZKE.

CERTIFICATE OF CORREOTI ON Patent No. 2,126,881.

August 16, 1958.

PAUL GA'I'ZK'E It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 3, second column, line 51, claim 10, for the word "were"read ware; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 27th day of September, A. D. 1958.

(Seal) Henry Van Arsdale Acting commissioner of Patents.

truck comprising in combination a truck body including a platform for acharge of ceramic ware, a container for a liquid hydrocarbon locatedbeneath said piatform, a resistance heating element in said container, acurrent collector for said heating element, and means to direct theheated liquid hydrocarbon in a substantially gaseous state into the coreof said charge.

PAUL GATZKE.

CERTIFICATE OF CORREOTI ON Patent No. 2,126,881.

August 16, 1958.

PAUL GA'I'ZK'E It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 3, second column, line 51, claim 10, for the word "were"read ware; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 27th day of September, A. D. 1958.

(Seal) Henry Van Arsdale Acting commissioner of Patents.

